Blade ring for a turbomachine

ABSTRACT

A blade ring for an axial turbomachine is provided, having a blade carrier with a number of retaining grooves and corresponding blades, the blade roots of which are inserted into the retaining grooves, wherein the blades, on the underside facing toward a groove base of the retaining groove, have a recess, the base of which is at least partially obliquely inclined relative to the groove base and in which recess is arranged one wedge-shaped clamping element for pressing the blade root against the support flanks. A spring element is provided in each recess, the spring force of which acts on the respective wedge-shaped clamping element along the retaining groove. Means are provided with which the wedge-shaped clamping element can be displaced temporarily into a position in which the blade root is seated in the retaining groove with play.

The invention relates to a blade ring for an axial turbomachine, comprising a blade carrier having a number of retaining grooves—having support flanks—for blades and a corresponding number of blades, the blade roots of which, which are configured in a manner corresponding to the retaining grooves, are inserted into the retaining grooves, wherein the blades have, on the blade root underside thereof facing toward a groove base of the retaining groove, a recess, the base of which is at least partially obliquely inclined with respect to the groove base of the retaining groove and in which there is arranged in each case a wedge-shaped clamping element for pressing the blade root against the support flanks.

A subject matter of the generic type is known, for example, from EP 1 892 380 A1. In accordance with the fastening of compressor rotor blades to a rotor as is proposed therein, two wedges are provided for each rotor blade between a blade root underside and the groove base of the retaining groove. The inclinations of the two wedges are in this case opposite. A clamping screw is screwed into the end of each wedge, making it possible on the one hand to achieve a radial prestressed positioning of the blade roots on corresponding support flanks of the retaining grooves. On the other hand, the screwed connection also serves to fix the rotor blades along the retaining grooves. Resilient fastening of the rotor blades is achieved by virtue of the fact that disk springs can be provided beneath the wedges.

It is perceived to be a disadvantage, however, that a screwed connection is used. On account of the comparatively harsh operating conditions and the operating temperatures which arise, screwed connections of this type may corrode, and therefore unproblematic disassembly cannot be ensured.

Furthermore, it is known from EP 1 703 078 A1, for example, to secure the rotor blades sitting in axial retaining grooves against displacement along the retaining grooves by using a securing plate. Here, a securing plate is positioned between the blade root and the retaining groove on the groove base. Through a bead on the securing plate, the latter engages into an opening provided on the root. After the blade has been inserted with the securing plate and the surrounding ends have been bent at the inlet and outlet sides of the root, form-fitting securing is achieved. In order to make it possible to ensure a sufficiently prestressed fit of the blade in the groove during operation, it is also necessary for the blade to be mounted with a prestress. Mounting with prestress leads to unfavorable wear and fretting at the support flanks, and this increases the risk of cracking. Primarily in the leading stages of a compressor exposed to axial throughflow, i.e. in the case of large blades, where particularly large prestressing forces are required, the mounting or disassembly proves to be difficult when servicing the blade.

It is therefore an object of the invention to provide a blade ring for a turbomachine, in which mounting of blades in the retaining grooves of a blade carrier without prestress and therefore with play is made possible, and nevertheless a sufficiently large prestress is present during operation which reliably avoids material-damaging wear—for example also through rattling.

The object directed to the blade ring for an axial turbomachine is achieved by the features of claim 1. Advantageous configurations are indicated in the dependent claims. These can be combined with one another in any desired way provided this is not expressly precluded by the dependency references indicated in the patent claims.

In the blade ring according to the invention for an axial turbomachine, comprising a blade carrier having a number of retaining grooves—having support flanks—for blades and a corresponding number of blades, the blade roots of which, which are configured in a manner corresponding to the retaining grooves, are inserted into the retaining grooves, wherein at least one of the blades, preferably all of the blades, has or have, on the blade root underside thereof facing toward a groove base of the retaining groove, a recess, the base of which is at least partially obliquely inclined with respect to the groove base of the retaining groove and in which there is arranged in each case a wedge-shaped clamping element for pressing the blade root against the support flanks, it is provided that each recess is provided with a spring element, the spring force of which acts along the retaining groove on the respective wedge-shaped clamping element, wherein the recess is delimited by a first side wall and a second wall located opposite the first side wall, wherein the spring element is supported on the one hand on the first side wall and on the other hand on an obtuse end of the wedge-shaped clamping element, and that provision is made of means with which, for mounting the blade in the retaining groove without prestress, the wedge-shaped clamping element can be displaced temporarily into a position in which the blade root sits in the retaining groove without prestress.

In the installed state, the spring element presses the wedge-shaped clamping element in the direction of its acute end, as a result of which, in combination with the inclined base of the recess, a force acts in the radial direction (with respect to the installed position in an axial turbomachine) on the blade root, pressing the latter against the support flanks of the retaining grooves. This effects play-free and at the same time prestressed fastening of the rotor blade in the retaining groove. The spring element is therefore supported on the one hand on a first side wall of the recess and on the other hand on the obtuse end of the wedge-shaped clamping element. In order to then make it possible for the blade to be disassembled from or mounted in the retaining groove without prestress, it is necessary for provision to be made of means with which the wedge-shaped clamping element can be displaced temporarily into a position in which the obtuse end of the wedge-shaped clamping element is closer to the first side wall than when in the mounted state. In other words: the spring element is compressed further than is provided for in the mounted state only for the duration of the disassembly or mounting. Through the corresponding inclinations of the base of the recess and of the wedge-shaped clamping element, the displacement of the clamping element toward the first side wall has a relieving effect for bracing the rotor blade on the support flanks of the retaining groove. This gives rise to play along the axis from the groove base of the retaining groove in the direction of the base of the recess which is present both for mounting the blade in and for disassembling the blade from the retaining groove and which in the meantime makes the desired handling of the blade without prestress possible. Consequently, it is also the case that no complex apparatuses are required for pressing the blade into the groove or pushing the blade out of the groove.

As a whole, what is thereby obtained is a simpler and quicker mounting and disassembly process which moreover ensures a high level of occupational safety for the fitter. At the same time, the magnitude of the spring force can be achieved by a simple variation of different spring elements. This is the case particularly when the spring elements are configured as disk springs or disk spring assemblies. At the same time, it is possible for the tolerance of the connection between the blade and blade carrier to be lowered to an average measure, making it possible to produce the components in a comparatively inexpensive manner.

During the operation of the axial turbomachine equipped with such a blade ring, this prestressing device is constantly adapted to the radial position of the blade. When formed from rotor blade rings, the blade will assume its maximum radial position in the retaining groove during operation under the action of the centrifugal forces. In parallel therewith, the wedge-shaped clamping element is pressed in further beneath the blade under the action of the spring force of the spring element. Therefore, a particularly high prestress of the blade is retained even when the rotational speed of the machine decreases. This limits the relative movements even of comparatively large blades and reduces the wear in the retaining grooves.

According to a first advantageous configuration, the spring element is in the form of a disk spring or disk spring assembly. At the same time, an opening is provided in the first side wall. At the same time, a cylindrical pin is arranged at the obtuse end of the wedge-shaped clamping element and extends both through the disk spring or the disk spring assembly and into the opening or through the opening in the side wall. By way of example, the cylindrical pin can be driven into a bore arranged on the clamping element or can be firmly adhesively bonded there. In conjunction with the opening arranged in the side wall, the cylindrical pin has the function of guiding the spring element and at the same time of securing the wedge-shaped clamping element, so that the latter cannot undesirably jump out of the recess during mounting.

According to a further advantageous development, the means comprises a threaded hole, which is arranged in the second side wall and into which a mounting screw can be screwed from the outside to displace the wedge-shaped clamping element toward the first side wall. Consequently, firstly the spring element is put over the cylindrical pin of the wedge-shaped clamping element before the blade is mounted, and then the cylindrical pin is introduced into the opening arranged in the first side wall. At the same time, the wedge-shaped clamping element is placed into the recess arranged on the underside of the blade root. Then, a mounting screw having a threaded shank of appropriate length is temporarily screwed in from the outside through the threaded hole present in the second side wall, said mounting screw making it possible for the wedge-shaped clamping element to be displaced in the direction of the first side wall. The displacement here has to be effected to such an extent that the wedge-shaped clamping element is countersunk completely in the recess, and mounting of the blade with the clamping element with play is thus possible. Then, the subassembly produced in this way is pushed into the retaining groove. Once the subassembly and therefore the blade have assumed the predefined position in the retaining groove, the mounting screw screwed into the second side wall can be released again, as a result of which the wedge-shaped clamping element is pressed in the direction of the second side wall by the spring element. On account of the inclined face of the wedge-shaped clamping element and of the base of the recess corresponding thereto, the wedge-shaped clamping element is pressed into the narrowing space between the groove base and the base, and comes to rest against both faces—the groove base and the base. As a result, the blade root is then braced against the support flanks of the retaining groove.

Instead of a threaded connection in the second side wall, it is also possible for a bayonet connection to be provided, for example.

According to a further preferred configuration, a plate-like securing element arranged between a blade root underside and a groove base of the retaining groove lying opposite the blade root underside secures each of the blades against displacement along the retaining grooves, in that the ends of the plate-like securing element bear laterally against the blade carrier. When axial securing of this nature is employed, the plate-like securing element is located between the groove base and the wedge-shaped clamping element.

It is further preferable that the wedge-shaped clamping element has an at least partially hollow form. This makes the fastening of the blade more elastic in the direction of prestress and additionally makes frictional damping possible.

It is further particularly preferable that the blade ring is a rotor blade ring, and therefore the blade carrier is in the form of a rotor disk or shaft and the blade is in the form of a rotor blade. Nevertheless, the blade ring is also suitable for fastening guide blades.

It is particularly preferable to use the blade ring in a compressor of a stationary gas turbine exposed to axial throughflow.

Further advantages and features of the invention will be explained in more detail on the basis of further exemplary embodiments. In this respect, further features and advantages will be indicated in the description of the figures. In the drawing:

FIG. 1 shows a stationary gas turbine in a longitudinal partial section,

FIG. 2 shows the longitudinal section through a blade ring in the region of a retaining groove with a blade inserted therein according to a first exemplary embodiment,

FIG. 3 shows the side view of the section shown in FIG. 2,

FIG. 4 shows a further side view of a retaining groove with a blade inserted therein, and

FIG. 5 shows a longitudinal section analogous to FIG. 2 for a second exemplary embodiment of a blade ring.

In all the figures, identical features are provided with the same reference signs. Even though the invention is described in detail hereinbelow with reference to a rotor blade ring of a gas turbine compressor, the invention can also be used in other turbomachines.

FIG. 1 shows a stationary gas turbine 10 in a longitudinal partial section. The gas turbine 10 has, in the interior, a rotor 14, which is mounted rotatably about an axis of rotation 12 and which is also referred to as a turbine rotor. An intake housing 16, a compressor 18, a toroidal annular combustion chamber 20 with a plurality of burners 22 arranged rotationally symmetrically to one another, a turbine unit 24 and a turbine outlet housing 26 follow one another along the rotor 14.

The compressor 18 comprises an annular compressor duct with compressor stages following one another in cascade in the latter and composed of rotor blade and guide blade rings 44. The rotor blades 17 arranged on the rotor 14 are supported by rotor disks and lie with their freely ending airfoil tips 29 opposite an outer duct wall 42 of the compressor duct. The compressor duct issues via a compressor outlet diffuser 36 in a plenum 38. Provided in the latter is the annular combustion chamber 20 with its combustion space 28, which communicates with an annular hot gas duct 30 of the turbine unit 24. Four turbine stages 32 connected in series are arranged in the turbine unit 24. A generator or a working machine (not illustrated in either case) is coupled to the rotor 14.

When the gas turbine 10 is in operation, the compressor 18 sucks in through the intake housing 16 ambient air 34 as the medium to be compressed and compresses this ambient air. The compressed air is routed through the compressor outlet diffuser 36 into the plenum 38, from where it flows into the burners 22. Fuel also passes via the burners 22 into the combustion space 28. The fuel is burnt there, with the addition of the compressed air, to form a hot gas M. The hot gas M subsequently flows into the hot gas duct 30, where it expands, so as to perform work, at the turbine blades of the turbine unit 24. The energy released in the meantime is absorbed by the rotor 14 and is utilized, on the one hand, for driving the compressor 18 and, on the other hand, for driving a working machine or electric generator.

FIG. 2 shows a section through a rotor disk 19 of the rotor 14 of the gas turbine 10 in the region of a retaining groove 21 extending in the axial direction. The rotor disk 19 therefore represents a blade carrier 46, in the case of which the retaining grooves 21 are distributed uniformly along the circumference thereof and in this respect extend in the axial direction of the gas turbine. The retaining grooves 21 have a dovetail-like cross section (FIG. 3, FIG. 4) and therefore each comprise two support flanks 23, against which correspondingly configured bearing surfaces 25 of a blade root 31 of the blades 27 bear. The blades 27 are in the form of rotor blades.

A recess 37 is provided on an underside 33 of the blade root 31 which faces toward a groove base 35 of the retaining groove 21. The recess 37 is delimited by a first side wall 39 and a second side wall 41 lying opposite the first side wall 39. In the direction of flow of a medium flowing through the compressor 18, the first side wall 39 is arranged on the inflow side and the second side wall 41 is arranged on the outflow side.

A plate-like securing element 43 with longitudinally slotted ends is placed in the retaining groove 21 between the underside 33 and the groove base 35. In the pairs of tabs which thereby arise at both ends, it is the case that at each end both a tab 45 is bent outward and a tab 45 is bent inward (FIGS. 3 and 4), blocking displacement of the blade 27 inserted in the retaining groove 21.

A wedge-shaped clamping element 47 having an acute end 49 and an obtuse end 51 is provided in the recess 37. Arranged at the obtuse end 51 is a cylindrical pin 53, onto which a total of four disk springs are threaded as a spring element 55 in the exemplary embodiment shown. The cylindrical pin 53 extends into an opening 57 arranged in the first side wall 39. The base 59 of the recess 37 is inclined with respect to the groove base 35 of the retaining groove 21, corresponding to the inclination of the upper face 61 of the wedge-shaped clamping element 47 as shown in FIG. 2.

Furthermore, a threaded hole 63 is provided in the second side wall 41 and—like the opening 57—extends parallel to the retaining groove 21. A mounting screw 65 required for mounting the blade 27 can be screwed into the threaded hole 63 and can be used to displace the wedge-shaped clamping element 47 to the left in FIG. 2 to such an extent that the obtuse end 51 thereof is positioned comparatively close to the first side wall 39. The wedge-shaped clamping element 47 can thereby be countersunk completely in the recess 37.

The blade 27 is then mounted in the retaining groove 21 as follows: firstly, the prefabricated plate-like securing element 43 is inserted into the retaining groove. The plate-like securing element 43 extends over the entire length of the retaining groove 21, with two of the tabs 45 already being bent on the inflow side or outflow side transversely to the longitudinal extent thereof. The outwardly bent tab 45 serves as a stop when the blade 27 is being pushed into the retaining groove 21. At the other end of the plate-like securing element 43, for the time being only one of the two tabs 45 is pre-bent in the radial direction toward the machine axis. Then, the spring element 55 is placed onto the cylindrical pin 53 of the wedge-shaped clamping element 47, and these are inserted together into the opening 57 and the recess 37. The cylindrical pin 53 then engages into the opening 57, which is in the form of an elongated hole. Once the inclined face 61 of the wedge-shaped clamping element 47 bears against the inclined base 59, the mounting screw 65 is then screwed into the threaded hole 63, to such a depth that the wedge-shaped clamping element 47 is pressed toward the opposite side, i.e. in the direction of the first side wall 39, to be precise until the wedge base 67 is located within the recess. It is thereby possible to ensure the insertion of the blade 27 without prestress. Then, the blade 27 is pushed into the retaining groove 21 with the prestressed wedge-shaped clamping element 47. After the blade 27 has been aligned in the retaining groove 21, the mounting screw 65 is released and removed from the subassembly. As a result, the wedge-shaped clamping element 47 is relieved of the force of the mounting screw and, through the action of the axial forces of the spring element 55, can press the blade 27 in the retaining groove 21 against the support flanks 23 thereof, and thus prestress it. Finally, the tab 45 of the plate-like securing element 43 which hitherto has not been bent is bent in the radial direction away from the machine axis, and this then secures the blade 27 against escaping from the retaining groove 21. If the blade 27 fastened in this way has to be removed from the retaining groove 21, the working steps are to be carried out in a reverse order. After one of the tabs 45 has been bent away, the mounting screw 65 is to be screwed into the threaded hole 63. As a result, the prestress is released and the blade 27 is relieved of load, after which it can then be easily pushed out of the retaining groove 21.

According to a second embodiment shown in FIG. 5, the wedge-shaped clamping element 47 can have an at least partially hollow form. The hollow space 69 brings about an elastic prestress and therefore additionally involves frictional damping.

As a whole, the invention relates to a blade ring 44 for an axial turbomachine, comprising a blade carrier 46 having a number of retaining grooves 21 and a corresponding number of blades 27, the blade roots 31 of which are inserted into the retaining grooves 21, wherein the blades 27 each have, on the underside 33 thereof facing toward a groove base 35 of the retaining groove 21, a recess 37, the base 59 of which is at least partially obliquely inclined with respect to the groove base 35 of the retaining groove 21 and in which there is arranged in each case a wedge-shaped clamping element 47 for pressing the blade root 31 against the support flanks 23. To make it possible to mount the blade 27 in the retaining groove 21 without prestress and to provide a blade ring 44 which can be used in operation without a screwed connection, it is provided that each recess 37 is provided with a spring element 55, the spring force of which acts along the retaining groove 21 on the respective wedge-shaped clamping element 47, and that provision is made of means with which, for mounting the blade 27 in the retaining groove 21 without prestress, the wedge-shaped clamping element 47 can be displaced temporarily into a position in which the blade root 31 sits in the retaining groove 21 without prestress. 

1. A blade ring for an axial turbomachine, comprising a blade carrier having a number of retaining grooves having support flanks for blades and a corresponding number of blades, the blade roots of which, which are configured in a manner corresponding to the retaining grooves, are inserted into the retaining grooves, wherein at least one of the blades has on the blade root underside thereof facing toward a groove base of the retaining groove, a recess, the base of which is at least partially obliquely inclined with respect to the groove base of the retaining groove and in which there is arranged in each case a wedge-shaped clamping element for pressing the blade root against the support flanks, a spring element provided in each recess, the spring force of which acts along the retaining groove on the respective wedge-shaped clamping element, wherein the recess is delimited by a first side wall and a second side wall located opposite the first side wall, wherein the spring element is supported on the one hand on the first side wall and on the other hand on an obtuse end of the wedge-shaped clamping element, and means for mounting the blade in the retaining groove without prestress, adapted such that the wedge-shaped clamping element can be displaced temporarily into a position in which the blade root sits in the retaining groove without prestress.
 2. The blade ring as claimed in claim 1, wherein the spring element is in the form of a disk spring assembly and an opening is provided in the first side wall, through both of which a cylindrical pin arranged at the obtuse end of the wedge-shaped clamping element extends.
 3. The blade ring as claimed in claim 1, wherein the means for mounting the blade comprises a threaded hole, which is arranged in the second side wall and into which a mounting screw can be screwed from the outside to displace the wedge-shaped clamping element toward the first side wall.
 4. The blade ring as claimed in claim 1, further comprising a plate-like securing element arranged between a blade root underside and a groove base of the retaining groove facing toward the blade root underside that secures each of the blades against displacement along the retaining groove, wherein the ends thereof bear laterally against the blade carrier.
 5. The blade ring as claimed in claim 1, wherein the wedge-shaped clamping element has an at least partially hollow form.
 6. A compressor for a stationary gas turbine comprising: at least one blade ring as claimed in claim
 1. 7. The blade ring as claimed in claim 1, wherein all of the blades have a recess on the blade root underside thereof facing toward the groove base of the retaining groove. 